The objective of the proposed research is to define and understand the role of humoral and cellular immune responses to specific Friend leukemia virus (FLV) polypeptides in the establishment and maintenance of dormant FLV infections in the DBA/2 mouse. We will use for this study a unique leukemia virus animal model in which we can stimulate active immune responses to FLV transformed cells in infected mice with a single injection of double stranded RNA from statolon, an extract of mycophage-infected penicillium stoloniferum. This dsRNA converts a rapdily fatal leukemia virus infection into a dormant state with prolonged clinical remission. The anti-FLV leukemia cell activities of antibodies produced by mice that have suppressed the development of FLV erythroleukemia will be studied both in vitro and in vivo using immunobiologic and molecular biologic techniques. A major goal will be to evaluate the role of antigenic modulation in the suppression of the FLV genome and the reestablishment of normal division in leukemic cells. We will identify the components of the immune response and of the FLV polypeptides to which they are directed. We will search for antibodies that bind virus induced polypeptides on the surface of spleen cells from mice and dormant FLV infections in order to determine the role of these antibodies in maintaining suppression of Friend virus erythroleukemia.